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07/02/2005 FCST: Central/Northern Plains

  • Thread starter Mike Hollingshead
  • Start date

Mike Hollingshead

http://www.wxcaster.com/modelskewt.php3?mo...&STATIONID=konl

Interesting setup for nc NE on Saturday. I'm thinking this could be a fairly big day, if not just one nice monster supercell dropping south. That sounding shows 7500 cape, but have been shown other soundings only showing 5000. Not that that matters as it's fairly clear there will be plenty. Not only that, but there is some really damn lovely shear, imo. NW flow at 500mb of 35 knots atop sse sfc flow of 15 knots. Toss in a boundary that runs n/s and doesn't have crazy convergence, but enough with high temps and I am very much game for this one. To me it is screaming isolated sup/s dropping south. Thought I'd start this for anyone brave enough to actually post forecast thoughts on here.
 
Interesting difference in forecast soundings, for example the CAPE, on Earl's site is much higher than the forecast sounding from Plymouth State College and the Storm Machine

Plymouth State College (CAPE much lower than Earl's)
http://vortex.plymouth.edu/cgi-bin/gen_grb...el&size=640x480

Storm Machine (Do not know if this link will work) (CAPE much lower than Earl's_
http://weather.admin.niu.edu/chaser/tempgif/31586.GIF
http://weather.admin.niu.edu/machine/fcstsound.html

College of Du Page Forecast Sounding (CAPE similar to Earl's)
http://weather.cod.edu/fsound/fsoundview.p...&lon=&site=KONL

Mike
 
This day is definately worth watching out for over the next 48 hrs...One thing to remember, the models begin to struggle with the transition from spring to summer, very inconsistant. Although we are not playing with a big ridge here, just something to remember...

Anyways, there will be a enough deep layer shear to support some nice rotating sups, if sfc winds stay backed, then probably enough low level shear to see some tornadoes. Fairly low lcl's will be nice. Boundary in play appears to be a fairly strong dryline...like said earlier, decent convergence. 700hPa temps are a little toasty, about 12C across central Nebraska with a little cooler temps across ne KS. The best vertical motion appears to be across ne KS. It will be interesting to see where the best moisture will setup.

Patiently waiting...
 
I really like the setup except for the low probability of a storm. The only problem is going to be the cap. If we can get a storm to fire though, it could be a good chase day. I am some what optimistic because of the added potential for an outflow boundary from overnight convection to increase convergence along the dryline. I will be chasing on Saturday if it looks like there is a reasonable chance of getting a storm. SPC doesn't seem convinced that it is going to happen, but I don't think anybody is going to have a clue what to expect until Saturday morning. I will post a forecast (or at least what I think is a forecast) tomorrow once I have a chance to take a closer look at things.
 
I agree, the setup looks fairly decent for Saturday, but the 700mb >14C cap will be a challenge to overcome IMO, but this is something worth monitoring.
 
12z eta has 700mb temps of 10-11c at 0z along the boundary. To me this seems like a great cap to have. 0z eta had convective temp of 92 at ONL while the 6z maintains it at 91. 12z eta coming in now and still looks good to me for around O'Neill NE, perhaps nw to start. Southerly sfc flow will be more than adequate with that flow aloft.
 
I see that the morning NAM run is more agressive with developing precip along the dryline, as well as having a well timed 500 mb shortwave passing over the area. 700 mb RH fields suggest the model has considerable lift all the way south to western KS to potential support a broken line of storms. Possible fly in the ointment is the tendency for NAM to overmix the eastward progress of the dryline - so this could leave the actual surface boundary much further west, where the capping inversion will be much stronger, LCL higher and low-level shear weaker and if the wave is correctly timed then it will possibly emerge too soon to aid in convection further west. Regardless, there seems to be plenty of reason to follow this system's potential for at least generating supercells somewhere in the Great Plains tomorrow.

Glen
 
I'm getting ready to head out from the DFW area to stay overnight in Liberal or Dodge City...Hays if I have the time. I am in total agreement with Mike H. for tomorrow and I see a good possibility for a couple of intense supercells to sprout anywhere from central regions of NE down into W KS. I like the area around Belleville, KS based strictly on model data and the trends. I'm sure things will change with the 00Z runs. :)

I've seen caps alot stronger than this busted with good dryline convergence. Given that the potential instability will be pretty volatile, once a weak spot is found in the cap, it'll be party time. With the forecast CAPE values in place, the vertical wind profiles look really great. As a storm starts moving more SE, the "eyeball" SRH values look pretty awesome to me. I'm pretty excited about it myself.
 
Im in agreement with a NW KS/SC NE target for tomorrow afternoon. 12z NAM is indeed much stronger with forcing towards 00z for convection, I am interested to see how the 18z-00z runs stack up against this. I like the same general area as Steve.. possibly a bit more west towards the Norton, KS area.. I also like the area in C NE. Wind fields are very sufficient for supercells .. tornado theat should increase thru the evening with lowering LCL's. 30-35kt mid-layer flow coupled with NW flow would allow a ESE/SE movement of convection into the higher SRH. This is of course all dependent on convection breaking thru.

Anyone notice how the SPC has completely dismissed the NE/KS setup on the new day 2? Edwards on the 6z made mention of the area.. the new outlook fails to even mention the setup.. away from brief mention in synopsis.... seems latest SPC wants to blow off the new 12z NAM.
 
I was actually pretty shocked by the SWODY2 until I noticed who wrote it.
That's all I'll say about that. :wink:

I'd say that it warrants a slight risk down into W KS...especially since now the 12z NAM wants to break out precip into that area...an area ripe for violent supercells.

I'm gathering my chase gear for what will likely be my last chase for the season until fall. I'll be heading up through the eastern TX PH into SW KS just in case there is something that pops up worth taking the lens cap off. I'm looking forward to it! I guess I'll see ya'll in the inflow. 8)
 
Anyone notice how the SPC has completely dismissed the NE/KS setup on the new day 2? Edwards on the 6z made mention of the area.. the new outlook fails to even mention the setup.. away from brief mention in synopsis.... seems latest SPC wants to blow off the new 12z NAM.
I don't exactly know what their reasoning is...their obviously have way more experience then I. Two concerns with this setup are: 1. Cap (but seems to be breakable) 2. Nam might be over-forecasting 500hPa flow (imagine that :lol: ) If you believe the GFS, the deep layer shear may not be sufficient for sups and it does not break out precip. The models are not in agreement, so it is tough to really make a reliable forecast. One thing I have noticed with the Nam with the past few systems is they look good 3 to 4 days out but, with each model run thereafter, it weakens the system (Shear wise). It has had a pretty good handle on moisture of late.

Will be looking for some consistency with the Nam...
 
Sounds like they're not trusting the NAM solution at all. Here's this afternoon's AFD from Sioux Falls, SD:

NOT QUITE SURE WHAT TO DO WITH AFTERNOON/EVNG ON SATURDAY. VIRTUALLY
NO CHANCE OF EVEN BEING CLOSE TO THE SFC-850HPA FORECAST DWPTS SAT
AFTN...WHICH RESULT IN NAM PRODUCING MASSIVE CONVECTIVE OUTBREAK DUE
TO -15/-13 SFC/850 HPA LI WITHIN CWA...BREAKING A FAIRLY GOOD CAP
TO DO SO. GFS ONLY SLIGHTLY LESS OFFENSIVE ON THE MOISTURE
FRONT...BUT KEEPS A BIT MORE CAPPING PREVAILING ACRS S. WHAT IS
OF LITTLE DOUBT IS THE FACT THE THERE WILL BE A GREAT DEAL OF SHEAR
WITH THE BAND OF WESTERLIES ALFT. HAVE A FEELING THAT LLJ IS
OVERESTIMATED AS HAS BEEN FOR MOST EVENTS THIS YEAR...AS REALLY
STRONG WAVE DOES NOT COME OUT UNTIL LATER SAT NIGHT INTO SUNDAY.
IF THE CAP GOES TO ANY GREAT DEGREE...WILL CERTAINLY OPEN THE DOOR
FOR ORGAINIZED CONVECTION...ESPLY ACRS THE NRN CWA.

I think I'll sit this one out as it'd be quite the drive from IL. :) Good luck to those a tad closer to the area.

Stan
 
NOT QUITE SURE WHAT TO DO WITH AFTERNOON/EVNG ON SATURDAY. VIRTUALLY NO CHANCE OF EVEN BEING CLOSE TO THE SFC-850HPA FORECAST DWPTS SAT AFTN...WHICH RESULT IN NAM PRODUCING MASSIVE CONVECTIVE OUTBREAK DUE TO -15/-13 SFC/850 HPA LI WITHIN CWA...BREAKING A FAIRLY GOOD CAP TO DO SO. GFS ONLY SLIGHTLY LESS OFFENSIVE ON THE MOISTURE FRONT...BUT KEEPS A BIT MORE CAPPING PREVAILING ACRS S. WHAT IS OF LITTLE DOUBT IS THE FACT THE THERE WILL BE A GREAT DEAL OF SHEAR WITH THE BAND OF WESTERLIES ALFT. HAVE A FEELING THAT LLJ IS OVERESTIMATED AS HAS BEEN FOR MOST EVENTS THIS YEAR...AS REALLY STRONG WAVE DOES NOT COME OUT UNTIL LATER SAT NIGHT INTO SUNDAY.IF THE CAP GOES TO ANY GREAT DEGREE...WILL CERTAINLY OPEN THE DOOR FOR ORGAINIZED CONVECTION...ESPLY ACRS THE NRN CWA.
Gotta say I know Jeff Chapman pretty well, and after talking to him about this, I mostly agree. Like i was discussing with him, into SESD and NCNEB, the cap is there, but with the forecast energy averaged between the Eta and GFS, it's certainly breakable. As a rough estimate, I think we're looking at between 7-11 PM for a bow type echo in SESD spawning from Supercells in a line from NC NEB (O'neill area) to N SD.

I think he summed it up very well when he said:
AFTER DISCUSSION WITH SEVERAL OTHERS...TOSSED OUT NAM SLN...AS
SUPER CONVECTION EFFECTIVELY RUINS THE ENVIRONMENT FOR REMAINDER OF
THE FORECAST FOR SAT NIGHT INTO SUNDAY. SLIGHTLY STRONGER CAP ON
GFS THIS TIME ARND...AND SEEMS THAT WLY PREFERRED FLOW WL BRING
PLUME OF MIXED LYR/CAP THRU AT LEAST NEBRASKA. BEST CHC FOR STORMS
SHUD BE ACRS NRN/NERN CWA DURING THE EVENING...FOLLOWING COLLOCATION
OF UPR DIV Q WITH JET ENTRANCE...AND RESPONSE OF VEERING LLJ.
 
Well it seems like the SPC is kind of discounting his theory when they said that things would be perfect for an MCS evolving as supercells moved from the Eastern SD region across SE SD into MN, and said that the best threat for isolated tornadoes will be over SE SD.

What? What's that I hear calling?
....It's getting louder....
CHASE DAY!
 
Well after looking at the 00z Nam, looks like SPC saw this one coming by not mentioning Neb or Ks. The cap looks to put a lid on anything developing in this area. Not even the low level jet can get things started in this region. Looks like the chase target would need to be shifted N into S Dak. Still looks like we will get some sups here. 997 sfc low helps out a lot, also getting into a breakable cap up here with 700hPa temps running around 10C. Looks like GFS had a handle on this day more than the NAM....Oh well :roll:
 
Yeah, that's what seperates the recreational forecaster from the professional - they always take the time to verify the initial conditions and are familiar with model biases and common feedback problems. Nevertheless, I still don't see tomorrow as a total wash for supercell potential particularly into northcentral NE given most recent NAM and GFS model guidance. 12-13C 700 mb temps are quite reasonable for this time of year given strong enough surface convergence and both models yield a weak shortwave passage through the area near peak heating. The strong surface convergence is what doesn't appear to exist in either run - but given the extent of ongoing convection in NE, there is reason to believe a decent boundary will be heading back north capable of interacting with the dryline and potentially kicking off storms somewhere in NE. That said, agree the likelihood of storms will be higher further north based on what appears available now - but I'd still want to get up in the morning and check the obs before making alternate plans for the day.

Glen
 
I don't think NE was slighted today either was it, up by Valentine? Was that supercell out by Sidney earlier this weak slighted? My target remains around or nw of O'Neill, probably closer to Ainsworth.
 
I think the forecast for tomorrow has been pretty well hashed out so I don't have a lot to add. The cap will be strong over Nebraska, but an ouflow boundary from overnight convection could increase convergence along the dryline and an isolated supercell or two are possible. I like the potential in Nebraska, but I am going with the safe bet in SE South Dakota. I think I will be able to get South in time if a storm should go up down in Nebraska. It looks like any tornado potential in SD should be later in the evening once the low and mid level winds improve. I was worried about the dewpoint gradient not being tight enough over SD, but I am not quite as worried about it anymore since the NAM shows it tightening up by 00Z. Forecast hodograph for Mitchell looks pretty good. LCL heights are a little high, but I won't let that stop me. I don't think we are going to get the dewpoints in the 70's that the NAM is forecasting since the good moisture resides all the way down in Oklahoma and Texas. The LLJ is going to have its work cut out for it. I would think we will come close to 70's with a few degrees help from evapotranspiration. I am still worried that LCL heights might be a little too high. I am planning on leaving by 7 tomorrow morning. Good luck to everyone who goes out.
 
I'm with you Mike! LOL!!

Seriously, does anybody here think that 15-17C 700mb temps could be busted and produce an awesome tornadic supercell? Go ahead and formulate your answer.

If you said "No way! That's a super-thermonuclear cap that nothing could bust through!!" or something to that equivalent, then you might want to go back and look at a few case studies...in particular June 13, 1998. There are plenty of other case studies. The common denominator is strong dryline convergence and or extremely steep lapse rates from 700-500mb. The cap is ALWAYS a concern...and if it isn't, then you are looking at convective chaos and storms erupting everywhere.

Ok...enough of my rant regarding cap strength. :wink:

Here's my thoughts. Take a look at the temps derived from the 00Z Sunday forecast over the NE region:

SFC 33C
850 26C
700 13C
500 -10C

The lapse rates from 850 up are extremely steep! Keep in mind that the dry adiabatic lapse rate is 10C/km.

850-700 = 8.67C/km
850-500 = 9C/km
and importantly...700-500 = 9.2C/km

What I see are increasing 700mb temps while the 500mb temps remain almost steady through the day. I certainly see the capping inversion being pretty thin albeit strong regarding a surface parcel. I think convergence will be strong enough to get the parcel through this capping inversion to convective nirvana.

I'm certainly not expectind a widespread event by any means. But, like Mike H., I do expect at least one or two big monster isolated supercells to erupt in NE tomorrow with a reasonable chance as far south as the KS/NE border. I'm more pessimistic about KS based on the latest model run.

Oh, but wait! We are talking about models, right? LOL!! I'm not hanging my hat on such subtle thermodynamics nor the surface configuration. The NAM has been horrible this year in most regards in my opinion. Models should only be used as "guidance" and not the "gospel". What happens if the 700mb temps are 1-2 degrees cooler? What if the dryline convergence is stronger? What if the impulse is a bit slower kicking out? I could go on about reasonable variances in the model forecasts. Of course, they could swing the other way and I'll find myself with a nice suntan by Saturday evening. :wink:

What I see is outrageous CAPE and lapse rates, moderate to strong convergence, pretty good vertical wind profiles (especially with such high instabilities)...and it is Nebraska. 8)

We will certainly be looking at numerous outflow boundaries too to make things fun. I'm convinced 7/2 will be a great chase day somewhere in NE.
 
Well, things certainly have changed a little since yesterday. The RUC/NAM squelch the dewpoints today more than I would have liked. Looking at current surface plots this morning, I still think upper 60Td are likely in KS into all of NE..especially with the aid of evapotranspiration. Of course, with surface temps progged to near 100F, that's some pretty serious dewpoint depressions. I'm hoping that surface temps in the lower 90's will be the case in NE today....we'll see.

An interesting thing I noticed this morning in the upper air analysis is the 500mb temps are certainly cooler than forecast with -10C all the way down into the TX PH and OK with -12C across NE. Upstream, -10C in CO and -12 in WY. So, I don't see these temps increasing to -8 to -9C today as forecast by the models across KS and NE. That's good news if we can keep the 500mb temps down to -10C. However, upstream 700mb temps are certainly toasty with 12 to 14C across WY/CO. It'll be interesting to see how the temps play out in the 700-500mb level today.

Vertical wind profiles still look better for NE and perhaps the KS/NE border region around Belleville. The convergence still looks great. It is interesting to note the big differences between the 12z RUC and NAM regarding surface features as well as the precip forecast with the RUC much more aggressive in breaking out a line of convection by 00Z and the NAM not even hinting at even a sprinkle. I'll take a compromise with a couple of big behemoth isolated cells exploding. :)

Gotta hit the road now from Liberal. See ya'll in the inflow.
 
I guess since the discussion here is focusing on whether NE will or will not see storms today, I won't try changing the topic. So, after review of morning conditions, still looks quite feasible for northcentral NE to see a storm today. While moisture is limited from what was forecast, the LLJ did manage to transport reasonable moisture, and LBF sounding shows favorable depth at that. Appears consistent with obs and model forecast that a weak dryline surge will emerge from out of ne CO into central NE, and so north of the center of this feature could see adequate convergence to initiate a cell or two. 700 mb temps look decent this morning - and no really strong WAA in the short term, perhaps yielding ~13 C over the initiation area, but with the current clear skies this shouldn't be too great a hurdle. With expected high cloud bases, tornado threat in the region could be limited, but certainly still there. I'd certainly want to watch moisture trends and see how things evolve, but I think Mike's early targets still look about as good as any until things mix out a bit more.

Glen
 
Chase target for July 2, 2005

Target:
Atlanta, NE (60 mi SW of Grand Island)

Timing:
Possible storm initiation between 5 PM and 6 PM CDT, with storms evolving into a broken line between O’Neill, NE and Hays, KS through 8 PM CDT. There is a chance that the area will remain capped and storms will never initiate.


Storm type:
Isolated supercells between 5 PM and early evening, with hail to 3â€￾ diameter the primary severe risk and wind gusts to 80mph a secondary risk. Expect impressive and photogenic storm structure from some of the storms. There is also a small chance for weaker tornadoes in a few of the storms. Storms will move slowly to the east at 15 mph. storms in this area should weaken or dissipate by late evening

Discussion:
Today, the atmosphere has recovered nicely from the overnight MCS’s in NE. At 18Z SFC dewpoints were generally AOA 60F along and E of a CNK/MCK/FIF line in NE, while dewpoints in the mid-60’s were found in the ODX/LNK area. 19Z visible satellite showed a developing CU field in CNTRL NE although it now appears as though initiation is several hours away given the slow evolution and elevated character of this field, despite convective temperatures in the low-90’s as indicated by 12Z LBF and OAX soundings. KLBF also showed a 70mb deep moist layer along with a large curve in the hodograph between the SFC and 500mb, although much of the curve below 900mb was in response to an outflow boundary.

WV analysis and 12Z UA charts showed several shortwaves moving to the SE in 30kt 500mb flow, with the wave to affect today’s WX now entering the NE panhandle. The real question is whether this feature is strong enough to force SFC convergence along a DL/confluence boundary over the next several hours. This primary shortwave appears to be well sampled by the RUC and NAM, while the RUC is much more aggressive in developing QPF. Given storm initiation, MLCAPE’s to 4500J/kg along with deep layer shear to 35 kts will support storm organization and severe potential. Hodograph curves will increase in the evening with increased backing of the surface winds.

- bill
 
Sitting here in Wakeeney, KS watching a nice line of TCu to my NW. This is starting to show up well in vis satellite. However, I'm not too crazy about the pitiful dewpoints...alot worse than I had expected today. KS looks like to me that the LCLs will be very high. I'm liking the NE surface obs right now...much more reasonable and of course better overall dynamics is here. So, I'm continuing heading north into NE. It looks like I'll be playing between Lexington and Ord.

Gotta run!!
 
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